Mission Completion
[Square], [Circle], [Triangle], [Square], [Circle], [Triangle], [Circle] while in any park. Then, when selecting a mission to play, press [Square] to get completion and unlock the next mission. If there are 3 medals, the first press of [Square] gets bronze, second gets silver, and third gets gold.

Hints

Unlockables
Do this during gameplay:

Easy friend ship - Tap [X] during chat menu instead of choosing which conversation is best.
Mini-games - Complete the game 100% to unlock the last 2 mini-games.
Faster romance - Play flirt mini-game instead of the regular conversation. Note: this only becomes avalible after you reach the love intrest level.